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Bridge-houses in steamers not covering engines and boilers may have an allowance not exceeding that which would be given for half the length of a bridge house of the same character covering engines ani boilers.
Para, 14.-In the case of a vessel having a forecastle and raised quarter-deck, the latter of less than the usual height, the length of raised quarter-deck to be allowed should be in proportion to its height as compared with the standard height. Thus L x H
= length allowed if the height is less than 4 ft. 4 When the combined length of the erections is ths of the length of the vessel, deduct 10 per cent. of the reserve buoyancy or 12 per cent. of the freeboard required for the flush-decked vessel after . correction for length.
When th of the length of the vessel, deduct 4 per cent. of the reserve buoyancy, or 6 per cent. of the freeboard required for the flush-decked vessel after correction for length. In cases where less than sth of the length of the vessel is covered by erections the allowance should be in proportion to that given for erections covering th of the length.
Para. 15:—When there is a poop only, the allowance is to be half of that which in this paragraph is given for a forecastle only of the same length. This is also applicable to a raised quarter-deck, subject to the modifications in the preceding note.
When the poop has no bulkhead, or the bulkhead does not extend across the vessel, one-half its length may be allowed, provided always proper freeing ports are fitted.
Para. 16. Sheer.-Sheer of a gradual character is to be defined as follows:
At fth the length of the vessel from the stem or sternpost the sheer is to be 55 per cent. of the sheer at stem or sternpost ; at th the length from stem or sternpost 26 per cent., and at Zihs the length 7 per cent. In cases where there is no forecastle the sheer is to be measured at the stem and sternpost, and corrections made for it in all respects as in the case of flush-decked vessels.
When the bridge-house is enclosed, the sheer should be taken at the ends and the freeboard corrected for sheer in estimating the allowance for erections. When the bridge-house is not enclosed at both ends, the sheer should be measured at Ath the length of the vessel, from the stem or sternpost, and the freeboard should not be corrected for sheer in estimating the allowance for erections.
Sub-para. (a).--Surveyors should note that clauses 11 and 12 apply either to vessels of the ordinary well-decked type or to vessels having a poop and forecastle with a disconnected bridge-house.
Sub-para. (f).-In flush-deck vessels the total standard mean sheer means the sheer measured at the stem and sternpost. in vessels having poops and forecastles, it means the sheer measured at points distant fth of the vessel's length from stem and sternpost.
In vessels obtaining an allowance for deck erections under para. 11, where the sheer drops abafı amidships, the height of the raised quarter-deck is to be taken from th: level of the top of the midship beam.
In applying the rule given in para. 16 (d), the extent of the depressed part of the sheer covered by deck erections is to be allowed for.
Para. 17. Round of Beam.-In flush deck sailing vessels the excess of round of beam, for which an allowance is made, shall not exceed the standard und of beam ; and for sailing vessels having erections on deck, the allowance shall be further reduced in pro. portion to the extent of the main deck uncovered.
TABLE A. The deductions for summer in vessels having deck erections is to be intermediate between those required by Tables A and C in proportion to the length of the ship covered by those erections.
Table B. All vessels equal in strength to Lloyd's spar-decked rule, or which, although in excess of that rule, do not come up to Lloyd's requirements for ships of full scantlings to the upper deck are to be considered as spar-decked ships, the freeboard for which will vary with their strength.
When the height between decks is greater or less than 7 ft., the consequent modification in freeboard will vary from rd to Grds the excess or deficiency of height, the exact proportion to depend upon the strength of the vessel.
In spar-decked vessels where the height between main and spar decks exceeds 7 st., the numbers for scantlings should be found assuming the height between decks to be 7 °1t.; if both these numbers are in the same grades as the actual scantling numbers of the vessel, the correction for height between decks is to be frd of the excess of height above 7 ft. If both the scantling numhers so sound are in higher grades than those of the actual vessel šrds of the excess of height is to be added, and if either one of these scantling numbers is in a higher grade, 1 of the excess of height is to be added. The same principle will apply in cases where the height between decks is less than 7 ft.
Since the freeboard is measured from the spar deck, it will be increased if the 'tween deck height is more, and decreased if it is less, than 7 feet.
In computing the freeboard of spar-decked vessels having scant. lings in excess of Lloyd's requirements, a comparison is to be made between their scantlings, the scantlings of vessels of the same dimensions classed 100A built to the three-decked rule, and of vessels built to the 100A spar-decked rule, and the freeboard is to be proportionate between that given in Table A and that given in Table B, alter deducting 12 per cent from the former ; but in no case must the freeboard so assigned be less than that provided in Table A for a vessel of the same dimensions, sheer, and camber, or round of beam, and deck erections.
In the comparison of scantlings and assignment of freeboard to spar-decked vessels having scantlings in excess of Lloyd's require. ments, the following method is to be adopted :
1. The difference between the freeboard by Table A (less 12 per cent.) and that by Table B to be divided by five, žths of it being considered with reference to the longitudinal strength, and Xths of it with reference to the transverse strength, these allowances to be the maximum deduction on each account.
2. In the comparison of steel ships, notwithstanding the general reduction of 20 per cent for steel, as compared with iron thicknesses, outside plating in the way of the double bottoms is not to be further reduced by oth unless its thickness is ths or over. No reduction is to be made in any case unless there are floors connected with every frame.
3. In the calculation of strength, the following method is to be adopted :(a) Thin iron or steel plating in decks and the inner plating of
double bottoms are to have their sectional area reduced for the purpose of the strength calculation as follows: Thickness in 16ths or 20ths 5 6 7 8
4 6 *7 9 (0) A deduction of th is to be made for rivet holes in steel,
and ith in iron, for the parts in tension. (c) Iron or steel decks which cover not less than ths of the
midship, length of the vessel are to be considered in the
calculation just as they would be if of the full length. (d) Wood weather decks, if continuous throughout the midship
portion of the ship, are to be considered as equivalent to
steel of sth the sectional area of the wood. (e) For the purpose of comparison of strength, the breadth of
the hatchways in the standard vessel shall be deemed to be grd the breadth of the deck, and the tie-plates should be assumed to be fitted at the side of the hatchways.
TABLE C. All vessels equal in strength to Lloyd's awning-decked rule, o which although in excess of that rule, do not come up to Lloyd's requirements for a spar-decked vessel, are to be considered as awning-decked vessels, the freeboard of which will vary with their strength.
No modification is necessary in respect of the height of 'tween decks of awning.decked vessels.
In computing the freeboard for awning.decked vessels having scantlings in excess of Lloyd's requirements, a comparison is to be made between their scantlings, the scantlings of vessels of the same dimension built to the 100 A spar-decked rule, and of vessels built to the 100A awning-decked rule, and the freeboard is to be proportionate between that given in Table B and that given in Table C.
In vessels where the superstructure is of less strength than that required for the 100A awning-decked class, additions are to be made to the freeboard in the same proportion.
The freeboard of awning-decked vessels of the highest class of less than 14 ft. moulded depth is to be arrived at as follows ::-
Ascertain the freeboard by Table A sor a vessel of the same moulded depth to main deck, and to reduce this by 'th the moulded depth, the result is the freeboard for awning-decked vessel.
The correction for length is to be lbs of an in. for 10 ft., and the deduction for summer voyages 2 in., and the addition for North Atlantic winter 2 in.
In the comparison of scantlings and assignment of freeboard to awning-deck vessels having scantlings in excess of Lloyd's requirements, the method of procedure to be similar to that stated above for spar-deck vessels having scantlings in excess of those provided by the spar-decked rule.
TABLE D. Sailing vessels classed A (black) in Lloyd's Register are to be regarded as first-class ships in applying the tables.
Hard wood ships, 1.l., other than fir or pine, classed A (red) in Lloyd's are to have their freeboards by the tables increased by 8 per cent.
Hard wood ships classed Æ in Lloyd's are to have their free. bourds by the tables increased 15 per cent.
Hard wood ships without class are to have their freeboards by the tables increased by 20 per cent., unless opened out for survey, when their freeboards will depend upon their condition.
Soft wood ships will require to have their coefficient of fineness modified in respect of the excess of the registered breadth caused by the extra thickness of side. That for hard wood ships is already provided for in the tables.
Soft wood ships classed A (red) in Lloyd's are to have their freeboards by the tables increased 10 per cent.
Soft wood ships classed Æ in Lloyd's are to have their free. boards increased 20 per cent.
Soft wood ships without class are to have their freeboards by the tables increased 25 per cent., unless opened out for survey, when their freeboards will depend upon their condition.
Iron and steel sailing vessels having a greater rate of rise of noor than 15 inches per foot of half breadth, may have the moulded depth to be used with the tables reduced by half the difference between the total rise of floor at the half breadth and the total rise at the standard rate of it inches per foot ; 2 inches per scot of half breadth is to be the maximum rate of rise on which an allowance is to be made. When the reserve buoyancy is calculated, the percentage taken shall be that corresponding to the depth reduced as above, but in no case shall the freeboard be less than that given in the top line of Table D for such percentage. Whichever method be adopted, the correction for length is to be applied in relation to the reduced moulded depth.
TURRET-DECK STEAMERS. RULES TO REGULATE THE DEPTH OF LOADING OF TURRET
DECK VESSELS AND VESSELS OF SIMILAR TYPES. The following agreement has been arrived at by the Conference of
the representatives of the Board of Trade, Lloyd's Register,
the British Corporation, and Bureau Veritas :-1.-A "turret " is a strongly constructed continuous erection at the middle line of a vessel, forming with the main or harbour deck an integral part of the hull, and of a breadth not exceeding sixten hs the greatest breadth of the vessel.
2.—The freeboard, calculated according to the rule given, is in consideration of the turret being cont nuous,
Where the turret is separated within the six-tenths length amidships, additional strength will be required to compensate for this.
3.--Hatch coamings at least 2 st. high, and casings to engine and boiler openings at least 4 ft. 6 in. high, to be fitted above the
4.-The volume of the turret to be estimated fiom a normal beam line drawn through the point where a vertical line at the quarter breadth of vessel cuts the upper surface of the vessel's deck. Where the turret is nearly one-half the breadth of the vessel, and its transverse section is or rounded form at its base, the base line of the turret to be drawn through the point where the vertical line at the quarter breadth cuts the upper surface continued in the same curve as the normal line of beam.
5.-The reserve buoyancy required by the tables to be estimated by laking 60 per cent. of the volume of the turret. The heigłt of the turret allowed for is not to exceed 25 per cent. of the moulded depth.
6.—The moulded depth of the vessel to be taken to be the depth a side from the beam line, as before defined, to the top of the keel.
7.- If a vessel has sheer, to determine the volume of the turret, the turret base line to be drawn at each section as described above. At the extreme fore-end of the vessel the base of the turret to be parallel to the turret deck.
8.--- No allowance shall be made for any erection above the turret except in respect of either a forecastle or poop, or both of them, provided that such allowance for poop or forecastle shall not exceed that due to a poop or forecastle equal to one-eighth of the length of the ship. The allowance to be in proportion to its length and the breadth as compared with the breadth of the ship at the after-end of the forecastle, or fore-end of the poop.
9.-The transverse and longitudinal strength of the vessel to be regulated by that required for a “three-deck spar-deck vessel of the same length, breadth, moulded depth, and co-efficient of fineness.
10.—Where a wood lower deck is required for the standard vessel, and the same is dispensed with, compensating strength must be furnished
11.-If the frame spacing be increased one-fourth, the thickness of all the plating, excepting garboard and sheer-strakes, should be increased by one-twentieth of an inch over the thickness required in the standard ship. Other increases in spacing should be dealt with in the same roportion.
12.-Should a vessel be constructed with a turret exceeding sixtenths the breadth of the vessel, or should the centre line of disc when ascertained reach a point above the junction of the vertical side with the rounded gunwale, full particulars and calculations with the proposed assignment to be submitted to the Board of Trade before freeboards are assigned.
13.—The freeboards in the certificates issued to be set off in feet and inches from the line of the tunet deck.